Devices for thermal treatment of products that are filled into containers, for example bottles, PET containers or cans, are known in the state of the art. These devices may comprise, for example, pasteurization systems, heat- or cooling devices. Also, these devices frequently appear in combination with multi-zone pasteurization systems in order to bring the products at least temporally on different, defined temperature levels. The heat exchange generally occurs through spraying with a process liquid such as water. Spraying shall be understood as sprinkling or irrigation of the containers. The water used in the process, which is also referred to as process water, is typically drizzled through nozzles above the product flow. The process water thereby releases heat to the product or absorbs heat due to the temperature difference. The used water is usually re-used, at least in part. There is a circulation mode for the process water.
In the process, contamination may occur in different ways in the pasteurization system, which may significantly impair the sprinkling system and eventually the functioning of the pasteurization system. For example, a biofilm may develop in parts of the system or in individual zones of that system. Biofilms consist, for instance, of a mucus layer (a film) in which microorganisms, such as bacteria, algae, fungi, etc., may be embedded.
Screening bands are typically used to eliminate particles, such as glass shards, sand and/or settling sediments from the process water. A screening band extending over several zones, as is used in many cases, has the disadvantage of requiring a horizontal band guiding system, so that the essentially vertical water flow accordingly leads to an extension of the machine height. This excess height may, for example, amount to 400 mm and constitute significant additional expenses in the area of the conveyor systems to feed and evacuate the containers. In case of a screening process per zone by respectively one screening band, the arising screening costs are disproportionally high. Plug-in screens are also used in simpler machines.
Both types of screens have the unfavorable effect of being obstructed for example by suspended sediments, mucilage and substances floating on the water. The mentioned materials stay, for example, on the screen surfaces where they accumulate. There, these substances increasingly hamper the throughput of the screens. Hence, the screens must be checked regularly for obstructions and cleaned. Especially if plug-in screens are used, the plug-in screens must, if appropriate, be pulled out and cleaned, meaning that the systems with plug-in screens lead to a high workload and/or staffing expenses. Typically, there are also attempts to dissolve suspended sediments, mucilage and substances floating on the water through chemical treatment. If, however, dissolving materials such as mucilage or similar substances through chemical treatment is not possible, or if there is a defect in the chemical water treatment process, the screen surfaces of the mentioned screen types will clog even more quickly.
The mesh size of a screen limits the attainable throughput rate. Typically, particles with a maximum size of 2-3 mm may be filtered with a band screen or a plug-in screen. Needle-shaped glass shards might still be able to pass such meshes, which may subsequently obstruct the nozzles for the sprinkling process. Furthermore, the nozzles as well as pump impellers are often made of plastic. Shards and other solid materials with a diameter smaller than 2-3 mm, however, may obstruct plastic nozzles from inside. A regular replacement of the nozzles is just as undesired as uncontrolled sprinkling due to ragged or lacerated nozzles, though. If, however, fresh water is used for the internal cleaning process, only cold water will be available in many cases. As the water used for purification is usually lost, there are additional water consumption costs. Also, cold water does not have the same cleaning power as warm water. A higher sprinkling pressure is consequently required for cold water. If the water from the sprinkling circuit is used, the removed dirt will accumulate in the plug-in screens and must be extracted manually at a later time. When the sprinkling processes are run, cleaning the areas below the water level is complicated due to the required water level in the respective zone of the system. To clean such an area, it is often required to let collected water flow away and then to manually clean these areas. In that case, however, fresh water with a high pressure is needed to be able to remove biofilms from the walls that are located under the water level. Hence, working hours, water and energy are needed to a large extent to clean this area. If, for example, biocide is dispensed in the deposit of a zone, the biocide is sucked up with the process water by the sprinkling water pump and drizzled over the areas to be cleaned. Areas that remain unsprayed by the sprinkling system or the treatment chamber above the sprinkling pipes are often heavily contaminated by a biofilm. After a cleaning process in which these areas are not reached sufficiently, these areas may lead to a repeated germ contamination of the pasteurizer. Then, they need to be cleaned again and possibly with extensive manual effort. The thermal sanitation process, which is often used, requires a considerable amount of thermal energy, especially to heat up practically the entire system and to bring all zones to the sanitation temperature. Hence, this entails a substantial expenditure of time beyond the production. Heating and action often require several hours. Typically, the pasteurization water shall be evacuated before. Consequently, sanitation requires the replacement of practically the whole water content of the system. Such filling and evacuation processes also require additional operating time and water consumption. Hence, this procedure is extremely costly for the operator in every respect.
In view of the problems cited above, the purpose of the present invention consists of providing a pasteurization system with purification of the process liquid, whereby the hygiene inside the system during treatment of the containers is improved and whereby a lower obstruction risk for the system is achieved so that the system becomes more efficient.